GB2251044A - Tube coupling - Google Patents

Abstract

A tube coupling for coupling a flexible tube or hose to another component has a male spigot 20 over which the tube is fitted and two clamping members 26, 28, one inside and one outside the tube wall, one being moveable and one stationary. When a tube 12 is fitted into the coupling, the clamping members move apart but when pull-out is attempted, the clamping members move toward one another and clamp the tube wall between them. <IMAGE>

Description

A TUBE COUPLING This invention relates to a tube coupling, and in particular to a coupling for use with soft, flexible tubes or hoses and which allows the tube to be fitted on the coupling by a simple push-fit action, but resists removal of the tube from the coupling.

There are conventional tube couplings which provide a male spigot over which the tube end is placed. An annular clip, a screw band clamp or a spring band is then secured around the tube where the tube is fitted on the spigot.

To make a joint in this way requires two operations; firstly pushing the tube onto the spigot and secondly fastening the annular clamp.

A tube coupling is also known from British Patent Application 2 051 280 in which a tube is fitted on a spigot and locked in place by a simple push-in action. In this case however pull-out of the tube is resisted by projections which are forced to bite into the material of the tube by a cam action between two parts acting against the outer surface of the tube. The use of projections which bite into the tube material can seriously weaken the tube and, under high pull-out loads the tube may tear where the projections bite into it.

According to the present invention, there is provided a tube coupling comprising a first component having a tubular spigot over which a tube can be fitted so that the internal bore of the tube communicates with and is sealed to the bore of the spigot, two clamping members mounted on the spigot, one being axially fixed and the other being axially moveable, so that when a tube is fitted over the spigot the surface of the tube makes frictional engagement with at least the axially moveable clamping member, and wherein axial movement of the tube in a pull-out direction causes the moveable clamping member to approach the fixed clamping member to clamp the tube therebetween.

The use of a clamping action rather than a biting action ensures that the tube is not damaged following pull-out forces.

The axially moveable clamping member may be mounted internally or externally of the spigot. Where the axially moveable member is mounted internally, the fixed member is mounted externally, and vice versa. Where the axially fixed member is mounted internally, then it may be formed by appropriate shaping of the external surface of the spigot.

The clamping diameters of the two clamping members may be such that the axially moveable member cannot move past the axially fixed member.

All the components of a coupling of this type may be made of a plastics material consistent with resistance to whatever fluid is to pass through the tube. Alternatively the spigot could be made of metal and other parts could be made of plastics materials.

The invention will now be further described, by way of example, with reference to the accompanying drawing, in which: Figure 1 shows a cross section through a first embodiment of tube coupling in accordance with the invention; Figure 2 shows the coupling of Figure 1 under the effect of pull-out forces: and Figure 3 is a cross section through a second embodiment of coupling in accordance with the invention.

Figure 1 shows a coupling 10 onto which a tube or hose 12 is fitted. The tube is fitted by pushing it in the direction indicated by an arrow 14 into an open mouth of the coupling, the open mouth being defined by the inner diameter of an outer, axially fixed clamping member 16. As the tube is pushed in, it meets and passes over the outer circumference of an axially moveable clamping member 18 and then over the outer diameter of a spigot 20. The diameter of a sealing lip 22 of the spigot 20 is chosen to give a good sealing effect with the inner surface of the tube 12, and the tube will be stretched slightly to achieve this seal. A joint can be made with this coupling in this way by simply pushing the tube 12 onto the spigot 20.

However in the event of pull-out forces in the direction of the arrow 24 (Figure 2) movement of the tube will also cause movement of the axially moveable member 18, because the outer lip 26 of this sealing member is of the same diameter as the lip 22. As the lip 26 of the clamping member 18 approaches the inwardly directed nose 28 of the outer clamping member 16, the wall of the tube 12 is nipped between the two clamping members and is held securely. The tube 12 cannot therefore be pulled off the coupling.

If the external diameter of the lip 26 is slightly greater than the internal diameter of the nose 28, then a clamping action is ensured whatever the thickness of the wall 12.

However with thicker tube walls, the diameter of the lip 26 may be less than that of the nose 28, and yet a good clamping action can be achieved.

Figure 3 shows an alternative construction. In this case, the axially moveable clamping member 30 is positioned externally of a spigot 32. A clamping member 30 has an inwardly directed nose 34 supported by a wire ring 36, and the spigot 32 carries an axially fixed clamping member in the form of a wedge-shaped region 38.

When the tube 12 is fitted into this coupling, the resilience of the tube allows it to be pushed over the wedge-shaped clamping member 38 and then under the nose 34 of the moveable clamping member 30. The nose 34 of the clamping member 30 will however be in frictional contact with the external surface of the tube 12 such that, when a pull-out force is exerted, the moveable clamping member 3n will travel with the tube to produce a clamping action between the nose 34 and the wedge shape 38.

In this case, when it is desired to remove the tube 12 from the coupling, the moveable clamping member 30 can be held back while a pull-out force is exerted, and in this case no clamping action will take place.

The invention provides a simple and effective quick-fit coupling for use with flexible tubes or hoses where clamping is effected by compressing the tube wall between two surfaces such that an increase in the pull-out force merely results in an increase in the compression exerted on the tube wall.

Claims (6)

Claims

1. A tube coupling comprising a first component having a tubular spigot over which a tube can be fitted so that the internal bore of the tube communicates with and is sealed to the bore of the spigot, two clamping members mounted on the spigot, one being axially fixed and the other being axially moveable, so that when a tube is fitted over the spigot the surface of the tube makes frictional engagement with at least the axially moveable clamping member, and wherein axial movement of the tube in a pull-out direction causes the moveable clamping member to approach the fixed clamping member to clamp the tube therebetween.

2. A tube coupling as claimed in Claim 1, wherein the axially moveable clamping member is mounted internally of the spigot.

3. A tube coupling as claimed in Claim 2, wherein the fixed member is mounted externally.

4. A tube coupling as claimed in Claim 1, wherein the axially moveable clamping member is mounted externally of the spigot and the axially fixed member is mounted internally and is formed by appropriate shaping of the external surface of the spigot.

5. A tube coupling as claimed in any preceding claim, wherein the clamping diameters of the two clamping members are such that the axially moveable member cannot move past the axially fixed member.

6. A tube coupling substantially as herein described with reference to any one embodiment shown in the accompanying drawings.